1. Field of the Invention
In the prior art, an air bag device, including an air bag module disposed on the steering wheel, has been used in practice. Such an air bag module is typically assembled in the steering wheel after the steering wheel is fitted to the top end of the steering column.
If a parting line, which outlines the external form of the air bag module, appears in an upper surface of the steering wheel, midway of the spoked portion of the steering wheel, the external appearance of the steering wheel is impaired. It is, therefore, known to extend the air bag module in a direction of the spoked portion, locating the parting line in the neighborhood of the outer end of the spoked portion. However, when the air bag module extends up to the neighborhood of the outer end of the spoked portion, the assembly structure required to assemble the horn switch in the steering wheel is made more complicated.
2. Description of Related Art
Accordingly, in Japanese Patent Publication No. 52-5128, a modular occupant restraint device is disclosed, which includes an air bag module and a horn switch. The air bag module is disposed on the steering wheel, and the horn switch is arranged laterally of the air bag module, between a cover member for the upper part of the air bag module and a baseplate of the air bag module. This makes it possible to operate the horn switch by compressing the cover member.
In this occupant restraint device, a baseplate extension is provided in the baseplate of the air bag module, and extends towards the spoked portion of the steering wheel. In a plastic case which receives therein the air bag module, a case extension is formed, extending up to the upper side of the baseplate extension. A V-shaped rib is formed at the bottom surface of the case extension close to the baseplate extension. A body portion of a ground connection clip of the horn switch, i.e., an electrode member, is disposed on the case extension, and a curved portion of the ground connection clip is disposed so as to contact the baseplate extension portion. The air bag is received in a space in the plastic case, and the case extension borders on the space in the plastic case.
In the modular occupant restraint device described in this publication, however, there are several problems. When the horn switch is pressed for operation, because there is insufficiently rigid support for the ground connection clip, the case extension portion will possibly be deformed downward. This results in the feeling of operating the horn switch being diminished, since a curved portion of the ground connection clip of the horn switch comes into contact with the baseplate extension. Also, because this contact constitutes a part of a grounding circuit of the horn switch, the operation of the horn switch becomes inferior, due to poor contact made by this contact portion.